Abstract

The hazards to nuclear power plants arising from large spills of liquefied natural gas (LNG) on water transportation routes are treated by deterministic analytical procedures. Global models, which address the salient features of the LNG spill phenomena are used in the analysis. A coupled computational model for the combined LNG spill, spreading, and fire scenario is developed. To predict the air blast environment in the vicinity of vapor clouds with "pancake-like" geometries, a scalable procedure using both analytical methods and hydrocode calculations is synthesized. Simple response criteria from the fire and weapons effects literature are used to characterize the susceptibility of safety-related power plant systems. The vulnerability of these systems Is established either by direct comparison between the LM threat and the susceptibility criteria or through simple response calculations.

The analysis and results indicate that the spreading of LNG vapor clouds up to the lower flammability limit Is dominated by gravitational effects. Severe fire and blast hazards occur only at locations directly engulfed by the LNG vapor cloud or in its immediate vicinity. Thermal loads resulting from an LNG fire are of short duration and can in general be tolerated by the safety-related power plant systems and components. On the other hand, blast loads from LNG vapor cloud explosions can cause severe damage to those systems. The safety standoff distance between the power plant site and the LNG spill location is primarily dependent on the wind- Induced LNG vapor cloud drift. Under strong wind conditions (8.96 m/s) it is estimated, that severe effects on the power plant may be experienced at distances in excess of 10 km in the down wind direction. To reach a no damage level under these adverse conditions a standoff distance of approximately 15 km may be required.